#include <iostream>
#include <fstream>
using namespace std;
ifstream inFile("flip.in");
ofstream out("flip.out");

int main()
{

	if (!inFile) {
		cout << endl << "Failed to open file ";
		return 1;
	}

	int n, m, i, j, sum;

	inFile >> n >> m;

	int** a = new int*[n];
	for (i = 0; i < n; ++i)
		a[i] = new int[m];

	for (i = 0; i < n; ++i)
	{
		for (j = 0; j < m; ++j)
		{
			inFile >> a[i][j];
		}
	}

	for (i = 0; i < n; ++i)
	{
		sum = 0;
		for (j = 0; j < m; ++j)
		{
			sum += a[i][j];
		}

		if (sum < 0) {
			for (j = 0; j < m; ++j)
			{
				a[i][j] *= -1;
			}
		}
	}

	for (i = 0; i < m; ++i)
	{
		sum = 0;
		for (j = 0; j < n; ++j)
		{
			sum += a[j][i];
		}
		if (sum < 0) {
			for (j = 0; j < n; ++j)
			{
				a[j][i] *= -1;
			}
		}
	}
	sum = 0;
	for (i = 0; i < n; ++i)
	{
		for (j = 0; j < m; ++j)
		{
			sum += a[i][j];
		}
	}

	out << sum;

	return 0;
}